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In chain-growth (or chain) polymerization, the only chain-extension reaction step is the addition of a monomer to a growing chain with an active center such as a free radical, cation, or anion. Once the growth of a chain is initiated by formation of an active center, chain propagation is usually rapid by addition of a sequence of monomers.
Branching may occur randomly or reactions may be designed so that specific architectures are targeted. [1] It is an important microstructural feature. A polymer's architecture affects many of its physical properties including solution viscosity, melt viscosity, solubility in various solvents, glass transition temperature and the size of ...
Step-growth polymerization can be divided into polycondensation, in which low-molar-mass by-product is formed in every reaction step, and polyaddition. Example of chain polymerization: Radical polymerization of styrene, R. is initiating radical, P. is another polymer chain radical terminating the formed chain by radical recombination.
Chain-growth polymerization or chain-growth polymerisation is a polymerization technique where monomer molecules add onto the active site on a growing polymer chain one at a time. [1] There are a limited number of these active sites at any moment during the polymerization which gives this method its key characteristics.
Combination of two active chain ends: one or both of the following processes may occur. Combination: two chain ends simply couple together to form one long chain (Figure 14). One can determine if this mode of termination is occurring by monitoring the molecular weight of the propagating species: combination will result in doubling of molecular ...
The original polymer chain is terminated and a new one is initiated. [6] The kinetic chain is not terminated if the new radical can add monomer. [1] However the degree of polymerization is reduced without affecting the rate of polymerization (which depends on kinetic chain length), since two (or more) macromolecules are formed instead of one. [7]
In polymer chemistry, chain transfer is a polymerization reaction by which the activity of a growing polymer chain is transferred to another molecule: [1] [2] + + where • is the active center, P is the initial polymer chain, X is the end group, and R is the substituent to which the active center is transferred.
The study of long chain polymers has been a source of problems within the realms of statistical mechanics since about the 1950s. One of the reasons however that scientists were interested in their study is that the equations governing the behavior of a polymer chain were independent of the chain chemistry.